This invention relates to a locking mechanism in a tension providing device.
Generally the "tension providing device" is a device to which a pushing force acts always in a constant direction and when an outer force acts in the counter direction against said pushing force, a characteristic nearly a rigid body is appeared.
The tension providing device is used for keeping a proper straining status continuously by pushing a chain or a belt with a pushing force having a certain direction, for instance, like a chain tensioner or a belt tensioner. In other words, the tensioner provides a certain tension to the chain or the belt pushing it in a certain direction when the chain or the belt is slackened due to the stretching or wearing during the employment. In this case, said device is desirable to have such characteristic as nearly the rigid body against the outer force in said pushing direction and the counter direction.
However, the tension providing device which satisfies the above demand is required to perform the readjustment or the like according to the elongation of the chain etc. In such case, the conventional tension providing device is obliged to be removed from the main body from the point of construction. When it is treated in a state attached to the main body, the winding of the spring is impossible without removing the lid of the casing which forms the shell of the device. Further, since the free return of the piston provided with the pushing force into the device is impossible even in case of removing the device from the main body, a reaction force always acts when the attaching bolt to the main body is slackened. Therefore, the removing work is very difficult.
Heretofore, such tension providing device is, for instance, constructed as shown in FIG. 1, and FIG. 2. The numeral 1 is a tension providing device wherein a shaft 4 is provided to a bearing 3 in casing 2 removably restricting the sliding in the axial direction. The shaft 4 is composed of a head portion 5 having a U type secton and a leg portion 6 extending outward from the bottom portion of said head 4a, the circumference of near the opening portion in said head 4a being provided with a female portion 5a and said leg portion 6 being provided with a spring 7 therein fixedly, an outer end of the spring 7 is fixed to the inner wall of case 2 suitably. The numeral 8 is a piston wherein a male portion is provided at one end thereof and another end is adapted to form a pillar 8a having a square in section. The male portion 8a of the piston 8 is secured with the female portion 5a of the shaft 4 and provided slidably in the axial direction being restricted the rotation by casing 2 supporting the pillar body 8b with the square bearing 9. At the spring 7 of the casing 2 and the opening the lid 10 is fixed with bolts 11 and 12.